Now when tests are run (via clojure.test/run-tests in either
the lein test task or manually in a repl/swank session), the
release-jeeps function will be replaced with a function that
returns [:jeep1] no matter what args it's called with.

Note that this replacement happens using alter-var-root, not
binding, so it will affect all threads, and it will not be
reverted at the end of the test run. This may be useful to help with
repl exploration.

Also note that the var's original value will be kept on the
:stubbs/original key in the metadata of the replacement in
case it's needed.